test: disable some varargs behavior tests on RISC-V due to LLVM 21 regression

#25064

Author: alexrp

test/behavior/var_args.zig

@@ -104,6 +104,7 @@ test "simple variadic function" {
     if (builtin.cpu.arch == .x86_64 and builtin.os.tag == .windows) return error.SkipZigTest; // TODO
     if (builtin.cpu.arch == .s390x and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/21350
     if (builtin.cpu.arch.isSPARC() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/23718
+    if (builtin.cpu.arch.isRISCV() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/25064
 
     const S = struct {
         fn simple(...) callconv(.c) c_int {
@@ -198,6 +199,7 @@ test "variadic functions" {
     if (builtin.cpu.arch == .x86_64 and builtin.os.tag == .windows) return error.SkipZigTest; // TODO
     if (builtin.cpu.arch == .s390x and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/21350
     if (builtin.cpu.arch.isSPARC() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/23718
+    if (builtin.cpu.arch.isRISCV() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/25064
 
     const S = struct {
         fn printf(buffer: [*]u8, format: [*:0]const u8, ...) callconv(.c) void {
@@ -250,6 +252,7 @@ test "copy VaList" {
     if (builtin.cpu.arch == .x86_64 and builtin.os.tag == .windows) return error.SkipZigTest; // TODO
     if (builtin.cpu.arch == .s390x and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/21350
     if (builtin.cpu.arch.isSPARC() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/23718
+    if (builtin.cpu.arch.isRISCV() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/25064
 
     const S = struct {
         fn add(count: c_int, ...) callconv(.c) c_int {
@@ -287,6 +290,7 @@ test "unused VaList arg" {
     }
     if (builtin.cpu.arch == .s390x and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/21350
     if (builtin.cpu.arch.isSPARC() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/23718
+    if (builtin.cpu.arch.isRISCV() and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest; // https://github.com/ziglang/zig/issues/25064
 
     const S = struct {
         fn thirdArg(dummy: c_int, ...) callconv(.c) c_int {